KSnapshot — KDE application for taking screenshots. It is capable of capturing images of the whole desktop, a single window, a section of a window, a selected rectangular region or a freehand region. Part of kdegraphics.

Xfce4 Screenshooter — This application allows you to capture the entire screen, the active window or a selected region. You can set the delay that elapses before the screenshot is taken and the action that will be done with the screenshot: save it to a PNG file, copy it to the clipboard, open it using another application, or host it on ZimageZ, a free online image hosting service. Part of xfce4-goodies.

zscreen — Lightweight GUI which allows you to take a screenshot of the entire screen or to select an area and then uploading the screenshot automatically to imgur. For taking the screenshot it uses scrot and zenity for the GUI.

Packages including a screenshot utility

GIMP — Image editing suite in the vein of proprietary editors such as Adobe Photoshop. GIMP ( GNU Image Manipulation Program) has been started in the mid 1990s and has acquired a large number of plugins and additional tools.

GraphicsMagick — Fork of ImageMagick designed to have API and command-line stability. It also supports multi-CPU for enhanced performance and thus is used by some large commercial sites (Flickr, etsy) for its performance.

ImageMagick — Command-line image manipulation program. It is known for its accurate format conversions with support for over 100 formats. Its API enables it to be scripted and it is usually used as a backend processor.

Screenshot of individual Xinerama heads

Xinerama-based multi-head setups have only one virtual screen. If the physical screens are different in height, you will find dead space in the screenshot. In this case, you may want to take screenshot of each physical screen individually. As long as Xinerama information is available from the X server, the following will work:

Screenshot of the active/focused window

The following script takes a screenshot of the currently focused window. It works with EWMH/NetWM compatible X Window Managers. To avoid overwriting previous screenshots, the current date is used as the filename.

GNOME

Note: If Prnt Scr complains about not finding gnome-screenshot or there is no "Take Screenshot" entry in your menu, you will need to install the gnome-utils package.

Other desktop environments or window managers

For other desktop environments such as LXDE or window managers such as Openbox and Compiz, one can add the above commands to the hotkey to take the screenshot. For example,

$ import -window root ~/Pictures/$(date '+%Y%m%d-%H%M%S').png

Adding the above command to the Prnt Scr key to Compiz allows to take the screenshot to the Pictures folder according to date and time.
Notice that the rc.xml file in Openbox does not understand commas; so, in order to bind that command to the Prnt Scr key in Openbox, you need to add the following to the keyboard section of your rc.xml file:

Virtual console

If you merely want to capture the text in the console and not an actual image, you can use setterm, which is part of the util-linux package. The following command will dump the textual contents of virtual console 1 to a file screen.dump in the current directory:

# setterm -dump 1 -file screen.dump

Root permission is needed because the contents of /dev/vcs1 need to be read.